Ramp and Magnetic Disk Device

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-063440, filed Apr. 10, 2024, the entire contents of which are incorporated herein by reference.

Embodiments described herein relate generally to a ramp and a magnetic disk device.

As a magnetic disk device, for example, a hard disk drive (HDD) comprises magnetic disks arranged to be rotatable, and magnetic heads that read and write information to and from the magnetic disk. The magnetic heads are moved by a head actuator between a load position on the magnetic disk and an unload position located on an outside of a respective magnetic disk. Further, the HDD comprises a ramp that holds the magnetic heads moved to the unload position. Generally, the ramp is molded from synthetic resin.

On the other hand, in recent years, the number of magnetic disks mounted on HDDs tends to increase as the capacity of HDDs increases. As the number of magnetic disks increases, the ramp as well tend to become larger. When a ramp has a larger size, a metal reinforcement plate may be embedded in the ramp for reinforcement in some cases.

Here, resin and metal have different coefficients of linear expansion. When the ramp is subjected to temperature changes, a difference in expansion occurs between the resin-made ramp and the metal reinforcement plate, thus causing thermal stress. Therefore, repeated temperature changes may cause cracks in corner portions of the resin part. If cracks occur, the dimensions of the ramp may shift, which may interfere with the loading and unloading operations of the magnetic heads.

Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, a ramp of a magnetic disk device comprises a ramp main body and a support bracket molded to be integrated as one body from resin and a metal reinforcement plate embedded in the ramp main body and opposing the support bracket. The reinforcement plate includes an opening which opposes a border portion between the ramp main body and the support bracket and is filled with the resin.

Note that the disclosure is merely an example, and proper changes in keeping with the spirit of the invention, which are easily conceivable by a person of ordinary skill in the art, come within the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the drawings show schematic illustration rather than as an accurate representation of what is implemented. However, such schematic illustration is merely exemplary, and in no way restricts the interpretation of the invention. In addition, in the specification and drawings, structural elements which function in the same or a similar manner to those described in connection with preceding drawings are denoted by like reference numbers, detailed description thereof being omitted unless necessary.

As a disk device, a hard disk drive (HDD) according to the first embodiment will be described in detail.is a perspective view of the HDD of the first embodiment, when a cover thereof is removed, andis a plan view of the HDD when the cover is removed.

As shown in, the HDD comprises a substantially rectangular-shaped housing. The housinghas a rectangular box-shaped basewith an open top surface and a cover (top cover)that is screwed to the basewith a plurality of screwsto close the top opening of the base. The baseincludes a rectangular bottom wallopposing the coverwith a gap therebetween, and side wallsformed to stand along peripheral edges of the bottom wall, which are molded to be integrated as one body, for example, from an aluminum alloy. The side wallsinclude a pair of long side walls opposing each other and a pair of short side walls opposing each other. The coveris formed into a rectangular plate shape, for example, from stainless steel. The coveris screwed to the top surface of the side wallsby screwsat its peripheral edge portions.

Inside the housing, there are a plurality of, for example, nine magnetic disksprovided as disk-shaped recording media, and a spindle motorthat supports and rotates the magnetic disks. The spindle motoris disposed on the bottom wall. The magnetic disksare each formed as a discoidal plate having, for example, 96 mm (3.5 inches) in diameter, and include a substrate made of a non-magnetic material, for example, glass or aluminum, and a magnetic recording layer formed on each of an upper surface (first surface) and a lower surface (second surface) of the substrate. The magnetic disksare fitted to the hub of the spindle motorcoaxially with respect to each other and are further cramped by a cramping spring. With this configuration, the magnetic disksare supported in respective positions parallel to the bottom wallof the base. The magnetic disksare rotated by the spindle motorin the direction of arrow B at a predetermined rotation speed. The number of magnetic disksmounted is not limited to nine, but may be eight or fewer, or ten or more.

As shown in, the housingcontains a plurality of magnetic headsthat record and reproduce information with respect to the respective magnetic disks, and an actuator assembly (, which may as well be referred to as a head stack assembly (HSA))that supports the magnetic headsto be movable with respect to the corresponding magnetic disks. Further, in the housing, there are provided a voice coil motor (VCM)that rotates and positions the actuator assembly, a ramp load mechanismthat holds the magnetic headin an unloaded position away from the respective magnetic diskwhen the magnetic headis moved to the outermost circumferential periphery of the magnetic disk, a substrate board unit (FPC unit)on which electronic components such as conversion connectors are mounted, and a spoiler. Note that the actuator assemblyand the VCMconstitute the head actuator.

To the outer surface of the bottom wallof the base, a printed circuit boardis fixed by screws. The printed circuit boardconstitutes a control unit that controls the operation of the spindle motor, as well as controls the VCMand the magnetic headsvia the board unit.

The actuator assemblyincludes an actuator blocksupported to be rotatable around a support shaft, a plurality of armsextending from the actuator block, and a suspension assemblyextending from each of the arms. The support shaftis provided to stand on the bottom wall. Each magnetic headis supported at a distal portion of each respective suspension assembly.

The actuator assemblyincludes a support frame, not shown, extending from the actuator blockin a direction opposite to the arm, and the voice coilis supported by the support frame. The voice coilis located between a pair of yokesfixed on the base, and these yokesand a magnet fixed to either one of the yokes all together constitute the VCM.

The FPC unitincludes a base portionfixed to the bottom wall, a slender belt-shaped relay portionextending from the base portion, and a joint portioncontinuously provided at a distal end of the relay portion. The base portion, the relay portion, and the joint portionare formed from a flexible printed circuit board (FPC). The joint portionis attached to the actuator block.

is a side view of magnetic heads and a magnetic disk in a levitated state.

As shown, the magnetic diskincludes a disk-shaped substratemade of a non-magnetic material, for example, glass. On each of the surfaces of the substrate, an underlying layer, a magnetic recording layer, and a protective filmare stacked in this order. The magnetic diskis rotated at a predetermined speed by the spindle motor.

The suspension assemblieseach include a suspension, a wiring member (flexure)mounted on the suspension, and a tabprotruding from the distal end of the suspension. The magnetic headis supported by a gimbal portionof the respective wiring member. The magnetic headis electrically connected to the FPC unitvia the wiring member.

The magnetic headis configured as a levitating head and includes a sliderformed into an approximately rectangular parallelepiped shape and a head portionformed at an outflow (trailing) end of the slider. The head portionincludes a write head and a read head. The magnetic headis maintained in a flying state by a predetermined distance from the surface of the respective magnetic diskby an air flow C generated between the surface of the disk and the sliderby the rotation of the magnetic disk. The direction of the air flow C coincides with the direction of rotation B of the magnetic disk.

As shown in, when the actuator assemblyis assembled into the base, the support shaftis provided to stand substantially parallel to the spindle of the spindle motor. The actuator assemblyis supported to be rotatable around the support shaftand can be pivoted between the unloaded position (position indicated by solid line in) where the respective magnetic headis unloaded to an outside of the outermost circumference of the magnetic diskand an inner circumferential position (position indicated by two dotted line in) where the magnetic headis located on the innermost circumferential side of the magnetic disk. Each magnetic diskis positioned between two suspension assemblies. When the HDD is in operation, the respective magnetic headssupported by the two suspension assembliesoppose the upper surface and lower surface of the magnetic disk, respectively.

The ramp load mechanismcomprises a ramp. The rampis fixed to the baseand located near the peripheral portion of the magnetic disk. When the HDD is not in operation and the magnetic headis moved out from the outer circumference of the magnetic diskto a predetermined unload position, the tabof the suspension assemblyruns on the ramp. In this manner, the magnetic headis kept in the unloaded position spaced apart from the magnetic disk.

Next, the rampof the ramp load mechanismwill be described.

is a perspective view showing a guide block side of the ramp, andis a perspective view showing a rear surface side of the ramp.

As shown in, the rampincludes a main body (ramp main body)formed into a rectangular plate shape, nine guide blocksprotruding from one surface of the main body, and a support bracketprotruding from the other surface of the main body, which are all molded to be integrated as one body, for example, from synthetic resin. In the figure, the height direction (first direction) of the rampis defined as the Y direction, the width direction (second direction) as the X direction, and the thickness direction as the Z direction.

The guide blockseach have a slender rectangular parallelepiped shape and extend in the width direction X. The nine guide blocksare aligned in the height direction Y, that is, the axial direction of the magnetic diskat predetermined intervals. At one end on a magnetic diskside of each of the guide blocks, a rectangular-shaped recess (notch)is formed. The recessesare formed over the main body.

Each of the guide blocksincludes an upper guide surface (first guide surface) Ga that guides and supports the tabof the respective suspension assemblyand a lower guide surface (second guide surface) Gb that guides and supports the tabof the respective suspension assembly. The upper guide surface Ga and the lower guide surface Gb are provided to oppose each other and approximately perpendicular to one surface of the main body.

The upper guide surface Ga and the lower guide surface Gb of each of the nine guide blocksare aligned with the heights of the corresponding suspension assemblies. Each of the guide surface Ga and guide surface Gb extends approximately in the radial direction of the respective magnetic diskto near the outer circumferential edge of the magnetic diskand is located on the route path of the respective tab.

The support bracketextends from the other (rear) surface of the main bodysubstantially vertically, that is, in the thickness direction Z. The support bracketis provided to stand approximately at a center of the main bodyin the height direction Y. The support brackethas a constant thickness Tin the height direction Y. The support bracketextends in the width direction X from one end of the main bodyin the width direction X to near the other end (the end on a magnetic diskside). Since a plurality of recessesare formed in the other end (one long side) of the main body, one end portionof the support bracketin the width direction X is spaced apart from the other end of the main bodyby a predetermined distance. The one end portionextends in the height direction Y by an equivalent amount to the thickness T. The one end portionmay as well be referred to as a border portion between the ramp bodyand the support bracketor a corner. In the direction of extension (width direction X) of the support bracket, the thickness of the rampin the thickness direction Z changes abruptly at the location of the one end portion

A sleeveis embedded in the support bracket. The sleeveincludes a central axis extending in the height direction Y and is opened in the upper surface and lower surface of the support bracket. A screw for fixing the ramp is inserted to through the sleeve. A positioning pinis provided to protrude from the lower surface of the support bracket(the surface of the base bottom wall). The positioning pinhas a central axis extending in the height direction Y.

is a perspective view of the rear surface side of the ramp andis a perspective view of the reinforcement plate.

As indicated by dashed line in, a metal reinforcement plateis embedded within the main body. The reinforcement plateis formed into a rectangular shape with dimensions slightly smaller than those of the main body, extends over substantially the entire surface of the main body, and opposes the support bracket. The reinforcement plateincludes a pair of long sidesandopposing each other. The pair of long sidesandextend in the height direction Y to be approximately parallel to the pair of long sides of the main bodyand are further spaced slightly inward from the pair of long sides of the main body, respectively.

As shown in, the reinforcement platecomprises an opening (clearance)formed on a one long sideside thereof. In this embodiment, the openingis made to open in the long side. In one example, the openingis formed into a rectangular shape. The openinghas a length tin the height direction Y and a width Win the width direction X.

With the reinforcement plateembedded in the main body, the openingopposes the one end portionof the support bracket. More specifically, the one end portionis located within an area opposing the opening. The openinghas an area larger than that of the one end portionto the extent that the lowering in strength of the reinforcement plateis minimized. Note that with the reinforcement plateembedded in the main body, the openingis filled with resin and forms part of the main body.

The distances between the one end portionand peripheral edges of the openingin plan view (when the main body is viewed from a direction perpendicular to the rear surface of the main bodyor the opening) are set as follows. In the height direction Y, the interval between the upper end of the one end portionand the upper edge of the openingis referred to as TU, the interval between the lower end of the one end portionand the lower edge of the openingis TL, and in the width direction X, the interval between the one end portionand the right edge of the openingis WR, the interval between the one end portionand the left edge of the openingis WL. In this case, the intervals TU, TL, WR, and WL are set larger than zero and smaller than an arbitrary upper limit, that is, in one example, the thickness Tof the support bracket. More preferably, for example, they are set to the relationships: T1/5≤TU, TL, WR≤T/, and T1/5≤WL≤T1×2/3.

Note here that the criteria for the intervals TU, TL, WR, and WL are not limited to the thickness Tof the support bracket, but various referential values can be selected. Alternatively, the intervals TU, TL, WR, and WL may be specified to be in a numerical range, for example, 0.5 to 3 mm.

In this embodiment, the main bodyand the support bracketare molded to be integrated as one body from resin, and the reinforcement plateis formed of a material different from resin, for example, metal. The resin can be, for example, polyacetal resin, liquid crystal polymer, or polyetherimide. As the metal, for example, stainless steel SUS304, stainless steel SUS430, aluminum alloy or the like can be used.

For example, in the case of a combination of polyacetal resin (coefficient of linear expansion: 11×10(1/K)) and SUS304 (coefficient of linear expansion: 1.73×10(1/K)), they differ in coefficient of linear expansion by a factor of 6 or more. The resin has a relatively large deformation against temperature, while the metal includes a relatively small deformation against temperature. Therefore, stress due to the difference in relative deformation occurs in the vicinity of the contact surfaces of the two. In the rampof this embodiment, on an assumption that there is not the opening, the effect by the difference in linear expansion coefficient is great in the support bracket, where a large amount of resin is involved and the contact distance with the reinforcement plateis long, and stress is likely to occur at one end (one end in the width direction X) of the support bracket, that is, one end (corner portion or border portion). In particular, due to the shape characteristics that the thickness of the rampin the thickness direction Z changes abruptly at the location of the one end portion, stress is likely to be concentrated at the one end portion

In order to avoid this, according to the present embodiment, the reinforcement plateis configured to be provided with the openinglocated in the area opposing the one end portionof the support bracket, and to fill the resin into the opening. In other words, there is no metal plate present in the area opposing the one end portion. With this configuration, the difference in relative deformation at the one end portioncan be eliminated, thereby making it possible to reduce the stress generated at the one end portion

is a perspective view showing a ramp installation portion of the housing of the HDD, and the ramp.

As shown in, the baseof the housingincludes a ramp installation portionon which the rampis to be installed, as an integrated one body. The ramp installation portionis provided to protrude as a mount portion at a corner portion between the bottom walland the side wallof the base. The ramp installation portionincludes a flat installation surface. The installation surfaceis located approximately midway in the height direction of the side walland extends approximately parallel to the bottom wall

The support bracketof the rampdescribed above is placed on the installation surfaceand is further secured to the installation surfaceby a fixing screw. The fixing screwis screwed into the installation surfacethrough a sleeveof the support bracket. The main bodyis positioned in an approximately vertical upright position with respect to the bottom wallof the base. Each of the guide blocksis located near the peripheral portion of the corresponding magnetic disk.

With the rampinstalled in the ramp installation section, the outer circumferential portions of the nine magnetic disksare positioned within the recessesof the corresponding guide blocks, respectively, each with a gap therebetween.

is a partially enlarged side view of a magnetic disk, magnetic heads, and the ramp. As shown, when the HDD is not in operation and the magnetic headsare moved out from the outer circumference of the magnetic disktoward the unloaded position, the tabof the suspension assemblyruns up on the upper guide surface Ga or lower guide surface Gb of the ramp. Further, the tabmoves along the upper guide surface Ga or lower guide surface Gb of the rampto the unload position and stops. As a result, the magnetic headis held in the unloaded position by the ramp, which is spaced apart from the magnetic disk.

According to the HDD of the first embodiment configured as described above, the rampis formed such that the openingis made in the reinforcement plate, so as to be located in an area opposing the one end portionof the support bracket, and the openingis filled with resin. With this configuration, the difference in relative deformation at one end portionof the support bracketcan be eliminated and the stress to be generated at the one end portioncan be reduced. Thus, it is possible to suppress the occurrence of cracks in the ramp.

As described above, according to the first embodiment, it is possible to provide a ramp which can suppress the occurrence of cracks and improve the reliability, and further a magnetic disk device comprising such a ramp.

Next, a ramp of an HDD according to another embodiment will be described. In the other embodiment provided below, parts identical to those in the first embodiment described above will be denoted by the same reference symbols, and their detailed descriptions will be omitted or simplified. The detailed descriptions will focus on parts that differ from those of the first embodiment.

is a perspective view showing a rear surface side of a ramp of an HDD according to the second embodiment, andis a perspective view of a reinforcement plate of the ramp.

As shown in the figures, a metal reinforcement plateis embedded in the main bodyof the ramp. The reinforcement plateis formed into a rectangular shape with dimensions slightly smaller than those of the main bodyand extends over substantially the entire surface of the main body. A pair of long sidesandof the reinforcement plateextend approximately parallel to a pair of long sides of the main bodyand are further spaced apart slightly inward from the pair of long sides, respectively.

The reinforcement platecomprises an opening (clearance)formed on a side of one long side. In the second embodiment, the openingis formed in a closed rectangular shape. That is, the openingis not opened to the long sideof the reinforcement plate. The long side of the openingopposes the long sideof the reinforcement platein parallel with an interval between them. A strip of metal plate extends between the long side of the openingand the long sideof the reinforcement plate.

With the reinforcement plateembedded in the main bodyof the ramp, the openingopposes one end portionof the support bracket. The one end portionis located within the area opposing the opening. Further, with the reinforcement plateembedded in the main body, the openingof the reinforcement plateis filled with resin so as to form a part of the main body.